Impulse-drive mechanism for magnetos



Dec. 1924- 1 1,520,207

. C, E. PEARSON I I IMPULSE DRIVE MECHANISM FOR MAGNETOS Filed Jan. 2, 1923 2 Sheena-Sheet 1 Z7 llvvswzbe:

Dec. 231, 1924. 1,520,207

c. E. PEARSON IMPULSE DRIVE MECHANISM FOR MAGNETOS Filed Jan. 2, 1923 2 Sheets-Sheet 2 hula-W702:

v Patented Dec. 23, 1924.

UNITED STA CARL E. PEARSON,

or CLEVELAND, orno, CLEVELAND, O'HIO, A CORPORATION or onro.

ASSIGNOR TO THE TEAGLE COMPANY, OF

IMPULSE-DRiVE mncnamsm FOR MAGNETOS.

Application filed January 2, 1923. .serial'no. 610,224.

To all whom it may concern:

Be it known that I, CARL E. PEARSON, a citizen of the United States, residing at Cleveland, in the county of Ouyahoga and State of Ohio, have invented certain new and useful Improvements in and Relating to Impulse-Drive Mechanisms for Magnetos, of which the following is a specification, reference being made therein to the accompanying drawings.

This invention relates to mechanisms such as are sometimes used for driving magneto type ignition generators of internal combustion engines, the mechanism being adapted to give the rotor of the magneto a quick rotary movement in order to secure adequate ignition currents even when .the engine is being, turned over slowly at starting. A

One of the objects of theinvention is-to provide an impulse drive mechanism simple and rugged in construction, easily assembled and disassembled and susceptible of being produced at moderate cost.

Another object of the invention is to increase the life of the drive and buffer spring structures of the impulse drive mechanism,

and render said mechanism more reliable in operation.

Anotherob ect of the invention 1s to provide an impulse drive mechanism of the automatic type with improved manually "controlled means for rendering the impulsing feature of the mechanism inoperative when desired. I

Various other objects more or less incidental or ancillary to the foregoingwill appear in the following description of preferred embodiment of my improvement, as shown in the accompanying drawings.

In the drawings, Fig. 1 is a side elevation of an impulse drive mechanism embodying my improvement.

- Fig. 2 is a frontelevation of the same.

Fig. 3 is a front elevation of the mechanism with some of the parts broken away and some shown in section. "*Fig. 4 is a vertical section on the line 4-4, Fig. 7. I

Figf5 is a fragmentary front elevation of the movable stop device and its securing means.

Fig. (Sisa fragmentary view showing the said movable stop device in section. Fig. 7 1s a section on'the line 7'7, Fig. 2..

against turning in relation to the shaft by "ing member'being operatively secured in Fig. 8 is a section on the line 88, Fig. 2.

Figs. 9, 10 and 11 are sections on the line 99, Fig. 7, showing the parts of the mechanism in the different relative positions which they assume in successive stages of the operation of the mechanism.

Fig. 12 is a section correspondingto Fig. 9 but illustrating a modified form of construction. I

Fig. 13 is also a section corresponding to springs fitted with its strip of felt.

Figs. 15 and 16 are a plan and end view, respectively, of the spring and felt.

Fig. 17 is a fragmentary longitudinal section through the spring and felt.

Referring in detail to the construction illustrated in Figs. 1 to 11,1 indicates the main frame or casing of the magneto ignition generator which may be of any preferred or known form of construction for magnetos. 2 is the rotor shaft of the generator which is formed with a tapered end in the usual manner to receive the driving connection. 3 is the driven member of the impulse drive mechanism mounted on the tapered end of the shaft 2 and secured the usual key 4. The said driven member comprises a 'hub part 3 and a disc or body part 3". On the outer end of the hub 3 is rotatably mounted the driving member 5 of the impulse drive mechanism, the said drivposition by a washer 6 and a nut 7, the latter being threaded on the end of shaft 2.

Obviously the nut and washer also serve to secure the driven member 3 against axial displacement on the shaft. On its outer face the driving member 5 is formed with the usual driving lugs 5 5 On the inner side of the driving member 5 is formed an annular channel 5 designed to receive the resilient force-transmitting means interposed between the driving and driven members. This force-transmitting means is in the form of two similar springs 8 and 9 and three balls 10, 11 and 12. The springs and balls are arranged in series relation as shown in Fig. 9 so as to form a resilient or spring structure disposed annularly in thedrivmg memberr5. Said drivmg member has its annular. channel 5 projection 13 having the opposite ends of the annular spring structure. The driving member also has 1ts annular channel 5". formed with an inwardprojection 14 which is normally engagedon one side by the ball 12 and thus serves as an abutment for one end of the spring 9. The driven member 3 has rigidly riveted to it an abutment pin which projects from the outer face of said member and fits between the balls 10 andll, the-relative dimensions of the parts being such that when the parts are in. their normalpositions as shown in Fig. 9 the balls 10 and 11 are in engagement with their abutments 13 and 13 and also substantially in engagement with. the abutment pin 15. At the same time the ball 12 is normally in engagement with the abutchannel, being retained after entering ment 14, the parts being normally held in these-relative positions by initial tensionof the springs 8 and 9. That is to say said springs are compressed somewhat when they are assembled. The channel 5* has its ra dially outward wall undercut as shown in Fig. 7- so as to retain the springs 8 and 9 and the balls 10, 11 and 12. The springs are small enough in diameter to readily enter tlhe 3' their tendency to spring or how outward. The balls, however, are of a larger diameter and nearly fill the channel. To permit their entrance into the channel the outer wall thereof is formed with entrance grooves 5 and 5. The outer face of the driven member 3, where it closes the channel 5" of the driving member, is formed with a shallow channel 3 to accommodate the springs 8 and 9 and the balls 10, 1'1 and 12.-

On reference to Fig. 9 it will be seen that the balls 10, 11 and 12, being seated in the end coils of the springs 8 and 9, serve to center the ends of the springs in the channel 5" and to hold several coils of each spring adjacent to its ends out of engagement with'the walls of the channel 5. The significance of this will be referred to below.

For urposes which will be more fully explained later I prefer to provide each'of the springs 8 and 9 with fibrous spacing means" between the coils. In the construction shown I accomplish this by threading strips of felt 16 and 17 back and forth between the coils of the springs 8 and 9, as more particularly illustrated in Figs. 14, 15, 16 and On the back side of the driven member 3 are mounted a pair of diametrically opposite centrifugally controlled dogs 18, 18. In the construction illustrated these dogs are in the form of pawls mounted on pivots 19, 19. In the same plane with these pawls, the driving member 5 is provided with rearers 13, 13", which ward cam flanges or extensions 20, 20. When the driving and driven members are turned slowly in the direction indicated by the arrow in Fig. 4, the longer, heavier ends 18 of'the pawls 18 successively move inward into engagement with the hub 3 and thus project the shorter ends 18 of the pawls outward beyond the periphery of the driving member so that said ends 18' are caused to engage a suitable stop which will presently be described.

The driving and driven members of the.

mechanism are partially surrounded by a casing 21 carried by the main frame or casing 1 of the magneto. The casing 21 can be joined to the frame 1 in any desired or suitable manner but in the preferred construction illustrated it is detachably secured to the magneto frame 1 by a plurality of screws 22. A close runningjoint is provided between the casin 21 and the cylindrical outer surface of the riving 'member 5 by a pair of plates 23, 24 and a packing ring 25 of felt, or the like, which is clamped between said plates and projects from the inner edges thereof into engagement with the outer surface of the driving member 5. The plates 23 and 24 are detachably secured to the cas- 7 its leaving only its central portion 27 effective I as a stop for the dogs 18. When the bolt 27 is in the position indicated in Figs. 3 and 8, the part 27 is in position to he engaged by the dogs 18, but by sliding the bolt out-' ward asindicated in Figs. 4 and 6 it is brought to'an inoperative position such that it' is not engaged by the dogs 18. To secure the stop normally in operative position the casing 21' is provided with a pivoted catch 28 mounted on a screw 29 and adapted to swing over the outer end of the stop 27 and hold it in operative position. To effectively secure the catch 28 in engagement with the stop 27, the latter has its outer end fitted with a screw 30 and the catch is formed with a notch 28 which is adapted to embrace the shank of the screw. Thus when the latch 28 is moved into operative position, as shown in Fig. 2, and the screw 30 is tightened on it,

the stop bolt and latch are effectively secured together so as to hold the stop in operative position. At the same time by simply loosening the screw the catch can be swung on its pivot to disengage the stop, and the latter of the screw 30.

can be moved endwise by grasping the head In the operation of the form of. apparatus above described, when starting the engine in connection with which the mag-- neto is used, the driving member 5 is turned, in the direction indicated by the arrows in theyarious figures of the drawings, at the relatively low speed corresponding to the speed of the engine. Referring to Fig. 9, as

the member 5 turns in' the direction of 'the arrow drivin force is transmitted from it through bal 11, spring 9, ball 12, spring 8, ball 10 and abutment pin 15, to the driven member 3 and in view of the initial tension of the springs 8 and 9, which is sufficient to overcome the magneto pull of the gene rator, the driven member is moved in unison with the driving'member until one of the dogs 18 engages the stop 27, as indicated in Fig. 3. Thereupon the rotary movement of the driven member is stopped while the movement of the driving member is ntinued. In Figs. 3 and 9, the parts are shown in the positions they occupy at the moment the dog 18 comes into engagement with the stop 27. As the turning movement of the driving member thereafter continues while the driven member remains stationary, the.

spring structure, comprising the springs 8 and 9, is compressed until the, parts reach the relative positions illustrated in Fig. 10 whereupon the cam 20, having moved from its full line position, as shown in Fig. 3, to its dotted line position, effects the disengagement of the dog 18 from the stop 27 and permits the driven member 3 to be snapped forward by the springs-8 and 9, thus causing the generation of an intense ignition current. At the end of the quick movement or impulse of the driven member and the magneto rotor ,the abutment pin 15, carried by the inertia of the driven member and the rotor, forciblyv engages the ball 11 and causes the latter to compress the spring 9 between itself and the ball 12 whichengages the abutas the engine speed exceeds a certain prede-.

t'ermined value the unbalanced centrifugal action on the longer ends 18 'of the dogs 18 serves automatically to retract the ends l8 so that they do not engage the stop 27. Under these conditions the driven member of the impulse mechanism turns in unison with the driving member, the initial tension .of the springs 8 and 9 being adequate to transmit the necessary driving force so that the relative positions of the parts indicated in Fig. 9 are maintained.

In the operation and use of my improved impulse mechanism two desirable functions are performed by the fibrous spacers 16 and 17 with which the springs 8 and 9 are provided. In impulse drive mechanism as previously constructed there has been considerable difficulty due to the breakage of the springs. I have discovered that this breakage of springs is in a large measure at least due to an unequal or nonuniform distribution of the load throughout the spring or springs and that this lack of uniform dis tribution of the load results, in the case of annularly disposed coiled springs, from the relatively large friction between the coils of thespring and the channel or casing in which it is mounted. In the present invention-I have overcome this difliculty in part by the use of the balls 10, 11 and 12 which, as above explained, hold the end coils of ,the springs out of engagement with the channel walls, the friction between the springs and the said walls being thus very materially reduced. However, even with the three points of support which the three balls provide for the annular spring structure at its two ends and. at its middle point, there still remains a substantial frictional engagement between the middle parts of the secured throughout the spring structure and" abnormal deflections with resultant straining and crystallizing of the spring material is avoided. Indeed, I have by means of my improved construction so greatly increased the life of the spring structure that a set of springs initially. free from defects will outlast other parts of the mechanism.

It will be understood that the impulse drive mechanism above described is entirely automatic in its operation. That is to say, when the parts are turned slowly, the drive member is intermittently stopped and then released and snapped forward with a quick movement but, as soon as the speed increases toa certain value the stop action ceases and the driving and driven members move in unison; Then if the speed again falls, as with the stopping of the engine, the stop dogs 18 return automatically to their operative positions in relation to the stop 27. Automatic impulse. mechanisms of this character as' heretoforev provided are somewhat troublesome in con nection with the timing of engines inasmuch as such timing involves the slow turning over of the engine by hand and this is interfered with by the engagement of the stop devices of the impulse mechanism. To overunderstood that the same reference numerals used in the foregoing description are applied to the like parts in Fig. 12, except in the case of the driving member 5'.

In the second 'modified form of construction illustrated in Fig. 13, the same driving member 5' is employed that is used in the modification of F ig. 12 but the ball 12 is omitted and a continuous single coiled spring 31 is substituted for the two springs 8 and 9 of the other forms of construction. In. all other respects the modification shown in Fig. 13 is similar to that first described bined effect of the ball support at the two and with the exception of the driving member 5 and the spring 31, the same reference numerals applied to the first form of construction illustrated are applied to like parts in Fig.- 13'. Y

It will be seen'that the construction shown in Fig. 12 has the advantage of the threepoint ball support for the. annular spring structure with consequent reduction in' friction between the said structure and the channel walls, just as in the case of the first described construction. In this respect the construction ilustrated in 13 is less desirable than either of the other two forms of construction since the ball supports are pro-. vided only at the two. extreme ends of the annular spring structure and the frictional resistance between the springs and the channel walls is of necessity greater- However, even without the third supporting ball for the middle of the spring structure the comendsand the fibrous spacer used in connection with the spring .31 enables me to secure betterresults even with the form of construction shown .in Fig. '13 than have been secured with any prior construction I known to me. 7

In both of the modifications shown in Figs. 12 and 13 .the entire annular spring "structure is subjected to the inertia shock of the mechanism as well as to the driving stress. I In this respect these two modifica-' tions are less to be desired than the first form of construction in which the entire spring structure including both the springs 8 and 9 are subjected to the load when the driving and driven members have their major. relative movement incident to the stopping of the driven member, while only the one spring-9 performs the function of.

a buffer to receive the shock of impact when the driven member is suddenly released. While it is possibleto use too short a spring for this buffer function, and serious breakage, in some prior mechanisms, has resulted from the use of buffer springs that were too short, it is also possible to have buffer springs too long to secure the best results.

Bearing in mind that the normal load transmitted through the impulse mechanism is suddenly increased and decreased twice during each revolution due to magnetic interaction of the rotor and stator of the magneto, it will be seen that if a relatively long and flexible buffer spring with a correspondinglylong periodis employed, the vibratory motion incident to the alternate forward snapping and buffing of the rotor will approach the relatively low speed of rotation more nearly than would, be the case with a shorter spring having a shorter period and said vibratory motion will therefore have a greater tendency to combine additively with the magnetic interaction between the rotor and stator so as to result in a rotary move- -ment of the rotor sufiiciently irregular to materially interfere with the timing of the engine. In a word, the best results are se- "cured where the buffer action is performed by a spring as short as may be used without danger. of breakage. In the first form of construction described, I secure an operation thatis very satisfactory in this respect and at the same time obtain the advantage of using only one form or size of sprmg, the two springs Sand 9 being alike, and interchangeable 1 My improved mechanism lends itself readhilyto manufacture. Obviousl the number difierent parts is relative small and these arereadil produced an in the production of the riving member the channel 5" is machined out and the abutment projections 13 and 14 are formed simply by" I withdrawing the milling tool which effects the undercut of the outer wall of the channel. It will be understood that the various parts of the mechanismare suitably hardened in order to insure adequate wearing qualities.

The mechanism is very easil assembled. 'Ihe balls and springs are rea ily inserted in the channel in the-driving member and 'theparts thus assembled are readily applied to the driven member by forcing the abut ment pin between the balls 10 and 11. Be-

cause of their universal symmetry the balls cannot become displaced in relation to the springs and as the balls are free to turn they are constantly presenting different surfaces for engagement with the various abutments thus obviating objectionable wear of the parts. The felt strips 16 are readily applied to the sprmgs and when once in position never become displaced because the coils of the springs become somewhat imbedded in the 'felt.. -further in connection with the felt spacers that in addition to their spacing function they serve to hold lubricant and 1n the rare cases of defective springs resulting in breakage they are adapted also to prevent displacement and entanglement of thebroken spring sections to such an extent as would render the mechanism inoperative.

It will be understood that my invention is not limited to the specific forms oi: construction which have been shown and described for purposes of explanation but that I the scope of the invention is indicated by the appended claims.

What I claim is: I

1.,In an impulse drive mechanism, the combination of a rotary driven member, a

- rotary driving member adapted to have a limited turning movement in relation to the driven member, means for intermittentdrivmg and driven members in such manmembers, and abutments cooperatively related to the springs and said driving and driven members in such manner that when relative rotational movement occurs between the driving and driven members in one direction force is transmitted from one of said members to the other through the entire series of springs and when such relative movement occurs in the opposite direction force is transmitted from one memher to the other through only part of said series.

2. In an impulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation to the driven member, means for intermittently stopping and releasing the driven mem her, two springs arranged in series relation between the driving and driven members, and abutments cooperatively related to the springs and said driving and driven members in such manner that when relative rotational movement occurs between the; driv-- ing and driven members in one direction in said channel between abutments on. sa1d force is transmitted from one of said members to the "other through the entire series of springs and when such relative movement occurs in the opposite direction force is transmitted from one member to the other through-one only of said springs.

It is to be observed coils .of abutments.

gaging said abutments,

stopping and releasing the driven member,-

a plurality of springs similar to each other and arranged in serles relation between the driving and driven members, and abutment-s cooperatively related to the springs and said driving and driven members in such manner that when relative rotational movement occurs between the driving and driven members in one direction force is transmitted from one of said members to the other through the entire series of springs and when such relative movement occurs in the opposite direction force is transmitted from one of said members to' the other through only part of said series.

4. In an impulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation to the driven member, means for intermittently stopping and releasing the driven member,

a plurality of coiled compression springs disposed in annular series between the drivmg and driven members, and abutments cooperatively related to the springs and said ner that when relative rotational movement occurs between the driving and driven members in one direction force is transmitted from one of said members to the other through the entire series of springs and when such relative movement occurs in the opposite direction force is transmitted from one of said members to the other through only art of said series.

5. Iii an impulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation to thedriven member, and resilient force-transmitting means disposed between abutments on the driving and driven members and comprising an annularly extending colled spring structure and balls seated in the end said structure and engaging said 6'. In an impulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation-to the driven member, one of said members being formed with an annular channel, and resilient force-transmitting means disposed driving and driven members and comprising a coiled spring structure .and balls seated in the end coils of said structure and enne diameter than the being greater in said balls and chanspring structure whereby the coils of the latter. adjacent the balls are held out of contact with the-channel walls.

7. In animpulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation to the driven member, one ofsaid members being formed with an annular channel, and resilient force-transmitting means disposed in said channel between abutments on said driving and driven members and comprisin a plurality of coiled springs in series re ation and balls seated in the end coils of said springs, the said balls and channel being greater in diameter than the springs whereby the coils of the latter adjacent the balls are held out of contact with the channel walls.

8. In an impulse drive mechanism, the combination of a rotary driven member, a; rotary driving member adapted to have a limited turning movement in rel ion tb the driven member, one of said members being formed with an annular channel, and resilient force-transmitting means disposed in said channel I and comprising two coiled springs in series relation, a single ball between two adjacent ends of said springs and two balls between the other two ends of said springs, one of said rotary members having an abutment interposed between said two balls and the other rotary member having abutments engaging said two balls and the single ball in such manner that when relative rotational movement occurs between said rotary members in one'direction force is transmitted from one member to the other through both of said springs and when such relative movement occurs in the opposite direction force is transmitted from one member to the other through only one of said springs. I

9. In an impulse drive mechanism, ,the combination of a rotary driven member, a rotary driving member adapted. to have a limited turning movement in relation to the driven member, one of said membersbeing formed with an annular-channel, and: resilient force-transmitting means disposed in said channel and comprising two coiled springs similar to each other and disposed in series relation, a single ball between two adjacent ends of said springs and two balls between the other two ends of said springs, one of' said rotary members having an abutment interposed between said two balls and the other rotary member having abutments engaging said two balls and the single ball in such manner that when relative rotational movement occurs between said rotary members in one direction iorce is transmitted from one member to the other through both of said springs and when suchrelative movement occurs inthe opposite direction force is transmitted from one member to the other through only one of said springs.

'10. In an impulse drive mechanism, the

combination of a rotary driven member, a-

combination of a rotary driven member, a

rotary driving member adapted .to have a limited turning 'movement in relation to the driven member, one of said members being formed with an annular channel and a shoulder projecting radially inward from the outer wall only of said channel, and

resilient force-transmitting means disposed in said channel between said shoulder and abutment on theothermotary member and comprising a coiled spring and a ball seated in'an end coil of the spring and engaging said shoulder.

- 12. In an impulse drive mechanism, the

combination of a rotary driven member, a

rotary driving member adapted to have a limited turning movement in relation to the driven member, one of said members being formed with an annular channel and a projection on one wall only of the channel formed with oppositely facing abutment shoulders, resilient force-transmitting means disposed in saidchannel and comprising a coiled spring structure and'balls seated in the end coils of said spring structure and engaging said shoulders on the rotary memher, and an abutment in the other rotary member disposed between and adapted to coact with either ofthe said balls.

13. In an impulse drive mechanism, the

combination of a rotary'driven member, a

rotary. drivingmember adapted to have a. limited turning movement in relation to the .driven member, one of said members being formed with an annular channel,'and resil ient force-transmitting means disposed in said channel between abutments on said driving and driven members and'comprisinga coiled spring having compressible fibrous material disposed between its coils andserving to ofier resistance to the collapse of the spring.

14. In an impulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation to the driven member, one of said members being formed with an annular channel, and resilram ient force-transmitting means disposed in said channel between abutments on said driving and driven members and comprising a coiled spring having a strip of compressible fibrous material threaded back and forth between the coils 'of the spring and serving to offer resistance to the collapse of the spring.

15. In an impulse drive mechanism, the combination of a rotary driven member, a rotary driving member adapted to have a limited turning movement in relation to the driven member, automatic means for intermoved out of operative position in relation to the dog, and manually disengageable means for normally holding the stop in operative position.

16. In impulse drive mechanism for magnetos, the combination with a magneto hav-- ing its drive shaft projecting from one side of its frame, of a rotary driving member, a

rotary driven member on which the driving member is supported and which is itself mounted on said shaft, a casing carried by the magneto frame and partially enclosing the driving and driven members and means for forming a running joint between 'the casing and the driving member comprisinga pair of annular plates secured to the casing and a packing ring clamped between said plates slidably engaging the driving member.

In testimony whereof, I hereunto aflix my signature.

CARL E. PEAR SON. 

